Views:22 Author:Site Editor Publish Time: 2020-12-04 Origin:Site
Plate heat exchangers (hereinafter referred to as plate exchangers) are often used as evaporators and condensers in heat pump cold and hot water units in the refrigeration industry.
In order to help users achieve better cooling effects, here are the main points of use and precautions in use of the plate converter used as a condenser. Let’s take a look.
The plate heat exchanger used as the evaporator in the refrigeration cycle of the heat pump unit is used as the condenser during the heat pump cycle. In both the refrigeration cycle and the heat pump cycle, the direction of refrigerant flow is opposite, while the direction of water flow remains unchanged.
Since the load of the condenser is greater than the load of the evaporator, the design should consider when the plate heat exchanger is used as an evaporator, it is forward flow heat transfer, and when used as a condenser, it is countercurrent heat transfer.
The determination of the inlet and outlet temperature of the cooling water of the plate converter should be determined according to the local meteorological conditions (mainly refers to the calculated temperature of the air-conditioning wet bulb in summer) and a comparison of investment and operating costs. Under normal circumstances, the inlet temperature of the cooling water is 4 to 6 degrees higher than the calculated temperature of the local summer air conditioning wet bulb, and the temperature difference of the cooling water is 4 to 6 degrees.
For the plate condenser, generally do not have the condensing section and the supercooling section coexist when choosing, because the heat exchange of the supercooling section is to exchange sensible heat, which is much lower than the latent heat exchange efficiency of the condensing section. If supercooling is required, in principle, a separate supercooler should be installed.
Since the condensation heat transfer coefficient is generally smaller than the water side heat transfer coefficient, in order to make the two as close as possible, the water flow velocity should be lower than that of the water-water heat exchanger, which can be initially selected from 0.3 to 0.6m/s. It is worth noting that the water flow speed should not be too small, otherwise it will cause low turbulence, resulting in unsatisfactory heat transfer efficiency and self-cleaning effect.
The heat transfer in the condenser basically occurs through film condensation, so the plate heat exchanger must be placed vertically. The refrigerant enters the plate condenser from the top in the form of superheated gas, and leaves from the bottom in the form of supercooled liquid after being superheated and cooled, condensed.
It should be pointed out that because the internal volume of the plate condenser is very small, it cannot store liquid. Therefore, the heat pump system with the plate exchanger as the water-side heat exchanger must be equipped with a liquid reservoir.
The main points of using a set of plate heat exchangers as condensers based on many years of experience are explained in more detail above. Users who intend to use the plate converter as a condenser can set it up in accordance with the above method. I believe that the effect will be better.